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I've noticed a metallic noise in my engine (possibly transmission?), but only while accelerating or cruising from 2000-2500rpm, but not at any other rpm. It's comparable to dragging a short length of chain under the front of the car, but fainter. My first though was burnt valves as my borla header broke a while back and has been leaking off and on (been repaired multiple times), but would burnt valves just make noise at the certain RPM range??? Anyone have any ideas what it could be?

BTW, it's a 1998 EJ22 with the 4EAT. Mods are GPMoto Short Ram, Borla Header, 2.25" exhaust with high flow cat and a universal muffler. Tranny fluid was changed (NOT FLUSHED) around 10k ago. Any help is appriciated.

yeah, it is something else. If it happens at certain rpm range, it is a loose item that is being shaken at its resonant frequency. It is like a woofer, playing the certain frequency note it is best at playing, the sweet spot so to speak. Certain frequencies will affect certain things differently due to their mass, shape, etc... pull and tap on items like the exhaust, hangers, heat shields, and other metal to metal items. check for broken tabs, loose screws, etc...

Could either be a loose heat shield or most likely the connection between the borla and the cat. Its very common with the borla header and stock cat to make a rattling noise. My old L does the same thing.

Or, it could be a small hamster with a hammer, and everytimme you go too fast, he starts smacking things inside your engine compartment. Hamsters can be very tempermental...

ROFLMFAO alrighty then

I was told that a leak so close to the heads could cause burnt valves, but I spoke with an ex-mechanic from my fire station on the phone and he said it doesn't sound like burnt valves to him, if anything to do with the engine. He told me burnt valves shouldn't really make any noise, but will cause misfires and lack of power instead. He said he's thinking one of the header pipes may have come loose inside the collector (it's wrapped with some leak patch stuff) and may be rattling due to resonance. I guess I'll stop worrying about it.